1. Field of the Invention
The invention relates to an image processing system and method for detecting a traffic indicator ahead of a vehicle.
2. Description of the Related Art
With improvement of the performance of on-vehicle cameras and evolution of information processing technologies, technologies have been proposed in which a vehicle detects the conditions around the vehicle and encourages the driver to perform an emergency operation to avoid a danger as needed, and performs an automatic vehicle control that, for example, brakes the vehicle (for example, see JP-A-10-177699).
In the technology described in JP-A-10-177699, during route guidance for the driver of a vehicle, a traffic indicator, such as a traffic signal, is detected from the data of images captured in the traveling direction of the vehicle when the vehicle is approaching a diverging point in the directed route, and the route guidance is then performed for the driver using the detected traffic indicator. In this technology, the regions over which the image processing is performed are limited to around diverging points, and thus it is possible to increase the speed of the image processing.
Also, technologies have been proposed in which, when detecting traffic signals, searching of traffic signals is performed over the region above the vertical center of each captured image, assuming that traffic signals are located several meters above the road surface (for example, see JP-A-2005-098853).
However, in JP-A-10-177699 describing the technology that detects a traffic signal, as a traffic indicator, which is located at or near a diverging point, there is no description regarding a method for estimating the position of a traffic signal. Traffic signals are often located at intersections and pedestrian crossings. However, if searching of traffic signals is performed over the entire region of the image captured at a diverging point of the directed route, the load of image processing is still large.
When searching a traffic indicator in an image, if the coordinate of the traffic indicator is known with a certain degree of accuracy, the speed of image data processing increases. For example, the three-dimensional position of a traffic indicator may be determined from an image or based on the position of the vehicle. In this case, the initial position of a traffic indicator is an important parameter. However, if the initial position is fixed at the region several meters above the road surface, the coordinate calculation diverges in some cases.